An electrostatic discharge (ESD) event refers to a temporary and abrupt flow of current between two objects of differing electrical potentials. ESD can be a serious issue for solid state electronic integrated circuits (ICs), as large potential changes and almost instantaneous current flows that occur during the ESD event can damage silicon junctions and oxide insulators. Typically, damage to an IC from the ESD event can diminish the performance of a silicon-based IC, or even render the IC unusable.
A buildup of charge on an object may occur for a variety of different reasons, many of which occur during the manufacturing and assembly of ICs. As a result, ICs may be subjected to inadvertent ESD events during assembly and prior to sale. To protect against ESD events, ESD protection schemes are implemented across the power supply rails of the IC. These ESD protection schemes typically include a clamping circuit that seeks to prevent the buildup of large electrical potentials within sensitive sections of the IC. In general, clamping circuits provide alternative pathways for a large current flow that may occur during the ESD event. These alternative pathways attempt to steer current around sensitive internal circuits, effectively bypassing the sensitive sections of the IC.